Middle School Chemistry, do me a favor, do me a favor, Middle School Chemistry

Composite materials are materials with new properties composed of two or more materials with different properties through physical or chemical methods on a macroscopic basis. Various materials complement each other in terms of performance, resulting in a synergistic effect, so that the comprehensive performance of composite materials is better than that of the original materials and meets various requirements. The matrix materials of composite materials are divided into two categories: metal and non-metal.

Metal substrates are commonly used in aluminum, magnesium, copper, titanium and their alloys. Non-metallic matrices mainly include synthetic resins, rubber, ceramics, graphite, carbon, etc. Reinforcement materials mainly include glass fiber, carbon fiber, boron fiber, aramid fiber, silicon carbide fiber, asbestos fiber, whisker, metal wire and hard fine particles.

Synthetic materials, also known as man-made materials, are materials that are artificially processed by chemical methods or polymerization of different substances, and their characteristics are different from those of raw materials, such as plastics, glass, steel, etc. Plastics, synthetic fibers and synthetic rubber are known as the three major organic synthesis technologies of the 20th century. Its inauguration has greatly improved the people's living standards, and its importance to the national economy and people's livelihood is self-evident.

This is the case.

A composite material is a material formed by mixing two or more materials, and a synthetic material is a material formed by the reaction of two or more materials. The former is a physical phenomenon and the latter is a chemical phenomenon.

It depends on the concentration of salt water to see if the eggs can float;

Physical Methods Distinguish:

1. Go to a small amount of solution to taste, salty is salted, tasteless is distilled water;

2. Distillation, if there are crystals, it is salt water, and if there are no crystals, it is distilled water;

3 Take a small amount of solution with platinum wire and burn it on an alcohol lamp, if the flame is yellow, it proves that the solution is saline, and the other bottle is distilled water.

4 Put it in the refrigerator, adjust the temperature to slightly below zero degrees Celsius, after a period of time more frozen distilled water, less or no freezing is salt water.

5) Each takes a small amount of imitation, energized, can conduct electricity for saturated salt fiber water, non-conductive for distilled water.

Chemical Methods Differentiate:

Respectively, go to a small amount of solution to put the old orange into the test tube, add nitric acidified silver nitrate solution dropwise to each test tube, if there is a white precipitate, the original solution is proved to be saline, and there is no phenomenon is distilled water.

Suppose the mass of hematite required is x tons.

The mass containing Fe2O3 is: 80% * x tons The mass containing iron is 80% x * 112 160 tons After the loss, the mass of iron is 80% x * 112 * 1 - 20%) 160 tons.

Corresponding to the mass of pig iron, there is an equation as follows:

80%x * 112 * 1 - 20%) / 160 = 700 * 1 - 4%)

Solve x = 1500

The plant needs 1,500 tons of hematite.

Requires 700t* pig iron 672t hematite with a chemical composition of Fe2O3

fe2o3--〉2fe

x 840t

x =840t*160/112=1200t

Solution: Let the mass of hematite be x

x*80%*70%*(1-20%)=700t*(1-4%)

It's so simple to ask questions, write your own reactive calculations, and you can't get used to it.

a:b Ratio of atomic mass = Ratio of actual mass of atom.

by: miniature submarine.

October 1, 2010.

At the same time, you are also welcome to join, and you are waiting for you to do what questions you can do at any time

1) Take a small amount of solid sample, add an appropriate amount of water, stir to obtain a colorless solution; Must be cuso4-free

2) Add a sufficient amount of BaCl2 solution to the solution obtained by experiment (1), and a white precipitate withered band is generated and filtered;

4) A sufficient amount of dilute nitric acid was added to the precipitate obtained in experiment (2), and the white precipitate was partially dissolved, and colorless gas was generated

Must contain Na2CO3 Na2SO4

3) add a sufficient amount of dilute nitric acid to the filtrate obtained by experiment (2) to make the solution acidic, and then drop into the agno3 solution, and a white precipitate is generated;

There are chloride ions, but they may be in the added BaCl2 solution or they may be in NaCl.

Therefore, it is judged that the original solid sample must contain Na2CO3 Na2SO4, must not contain CuSO4, and may contain NaCl and Kno3

From (1), it can be concluded that it does not contain CuSO4 because Cu2+ is blue.

From (2), it can be concluded that the solution contains SO42-sulfate ions, and the sulfate ions react with BACL2 to form barium sulfate. So it must contain Na2SO4

From (3), it can be concluded that the solution does not contain Na2CO3, because the sodium bicarbonate will react with dilute nitric acid to form sodium nitrate and carbon dioxide gas.

From (4), it can be concluded that the white precipitate is AGCL

So the sample must contain Na2SO4, must not contain CuSO4, Na2CO3, may contain NaCl, Kno3, because from.

The answer to the original question cannot be judged.

Must contain Na2CO3, Na2SO4, must not contain CuSO4, may contain NaCl, Kno3.

Solution: (1) Comparing the symbol of the world and its valence, it can be seen that the valency value is the same as the ion value, and its symbol, that is, positive and negative, is also the same

2) The writing of chemical formula is mainly based on the general law of chemical formula writing, the positive valence is arranged in front of the negative valence, and the algebraic sum of the valency is guaranteed to be zero

3) Use the ion symbols H+, Na+, and SO42- to determine that the valency is +1, +1, and -2 respectively, and then combine the algebraic sum of the valency of the elements in the compound to be zero, as well as the general law of chemical formula writing

4) Ferrous sulfate is composed of ferrous ions and sulfate ions, and the symbol of the cation contained is Fe2+

Therefore, the answer is: (1) electric limb and grandson; (2) valency; (3) MgSO4 (or NaCl); （4）fe2+．